The hydronic heating system used to heat homes and other dwellings has been in existence for many years and despite the development of many other hot air systems still remains a reliable and efficient means of heating. Generally in these systems, water is heated in a boiler and is pumped or forced under pressure throughout a myriad of pipes interconnected between each room in the building. As the hot water collects in one or more of the basins or radiators attached thereto, the metal pipes get hot and warm the surrounding air.
It is very important in these systems to keep the pipes full of water at all times. However, due to the expansion and contractions of water as it is heated and cooled, provisions must be made in the system to accomodate this. As the system temperature changes, the water in the system expands and contracts at a different rate than the metal that contains it.
As a result of the need to provide space or room for expansion, a necessary development was the expansion tank which is an accessory reservoir attached to the boiler. U.S. Pat. Nos. 4,414,464 to Cloutier and 3,627,203 to Martin are both indicative of the known state of the expansion tank art and their use in hydronic heating systems. These patents are hereby incorporated by reference. Generally, the tank is half filled with water with the remaining space occupied by air. This air space provides room for expansion/contraction of the water. The problem that arises however, is that water absorbs air slowly over time and as the air volume is reduced there is a corresponding reduction in the pressure that is produced thereby and is responsible for keeping additional water out. As more water enters the tank it eventually reduces the air cushion in the expansion tank to a point where no provision for water expansion is left. Furthermore, the water in the expansion tank is constantly circulating between the tank and the boiler and as it does, it carries the tank air out into the rest of the system. The air that gets into the system results in the often unsettling knocking and gurgling noises in the pipes with which everyone is familiar.
Another problem that arises by the removal and absorption of air by water is that the expansion tank eventually becomes completely filled with water and flooded and as a result no leeway exists for expansion. In the past, in order to alleviate the problem, air has to be pumped back into the tank. Numerous devices have been developed for collecting expansion tank air which is then pumped back into the expansion tank. Some devices collect the air as it is released in the boiler others collect it at some point in the system's pipes and pump it back to the tank. These are marginally effective however, and require the use of air vents on all the radiators, pipes and the boiler. Other manual means of pumping air back into the system requires drainage of the system, pumping air back into it and refilling the boiler and pipes which is both time consuming and costly. This unfortunately, is what is most often required.
The present invention is a means to put air back into the expansion tank without having to drain the entire system and later refill it. Other attempts to do this have been made in the past but nowhere are the results achieved in such a simple and efficient manner.
U.S. Pat. No. 4,013,221 to Eder entitled Pressure Balancing Device for Heating Systems discloses an expansion tank with a number of internal chambers which are connected to a heating system by feed and drain pipes whereby the flow of water into and out of the expansion tank is regulated by a valve and a pump. The pressure sensitive device actuates the pump to force water from the expansion tank to the heating system when there is a drop in pressure in the system. The device also detects when there is too much pressure in the system and opens the solenoid valve so that water can escape back into the expansion tank. The device works by means of a bellow within the expansion tank which is in contact with the outer air. The invention is directed to the regulator device which monitors pressure and water problems rather than solves them. There is no appreciation of the problems resulting from flooded expansion tanks nor is there any suggestion of any means to cure the problem.
U.S. Pat. No. 4,424,024 to Wilson, et. al. discloses a conventional heating system whereby an expansion tank is in operative communication with a furnace or hot water storage unit so that any back up of water or expansion thereof from the boiler unit is released to the expansion tank wherein it is contained. Any subsequent drop in pressure in the heating system results in a release of the water back to the boiler unit.
U.S. Pat. Nos. 4,301,320 to Hochstrasser, et. al. and 4,417,871 to Tarumi, et. al. also disclose conventional expansion tanks with release and/or drain valves as a part of heating systems known in the art. As before, neither of these patents appreciate the problems inherent in expansion tank flooding and the alleviation thereof. Valves and drain cocks are disclosed which presumably are used to drain the entire system as is known in the art.